Poisson problem

Say I have 11 days daily values representing the amount of cheese eaten by a lonely mouse every day. Next, based on those values I calculate the percentage of cheese eaten each day and I calculate the average (Lambda) of the 10 daily percentages observation period. The Poisson random variable (X) is 1 (representing one 10 day period).

Furthermore, I use the Poisson formula to calculate the cumulative probability [P(X ≥ x)] to learn what percentage (Lambda must, of
course, be positive) of cheese I can expect this pesky mouse to eat
daily in a given 10 day period.

QUESTIONS
1) Is the above problem correctly formulated?
2) To calculate the cumulative probability for a X=2 and thus learn what the percentage would be for a 2 ten days period, I would simply enter 2 as the new value of the Poisson random variable, and so on. Is this correct?
Thanks